With the recent remarkable development of medical electronics, remarkable progress has been made in novel diagnoses by ME apparatus such as CR (computer radiography), CT (computer tomography), US (ultrasonic diagnosis), RI (radioisotopic medicine) and thermography.
Unlike the conventional diagnostic process for directly obtaining a picture on X-ray photographic material, these diagnoses comprise outputting various measurements to a display from which a medical doctor can make a diagnosis. In the most actual diagnosis, however, a medical doctor does not only make a diagnosis from the display but also takes a picture on a recording material such as X-ray photographic material which will be developed for subsequent re-diagnosis in another place at another time. It has thus been desired to provide CRT photographic materials which can provide a faithful reproduction of a CRT display.
High temperature rapid processing has suddenly become popular in the process for the development of photographic materials. Thus, the time required for various photographic materials to be processed in an automatic developing machine has been extremely reduced. This rapid processing requires that a developer which can accomplish sufficient sensitivity in a short period of time be used and the photographic material used exhibits film properties such that it shows a rapid progress of development, provides a sufficient degree of blackening in a short period of time and dries in a short period of time after rinsing.
A typical approach for improving the dryability of the photographic materials comprises adding a sufficient added, amount of a hardening agent (gelatin crosslinking agent) during the coating step so that the emulsion layer or hydrophilic colloidal layer exhibits a reduced swell in the subsequent development, fixing and rinsing steps, resulting in the reduction of the water content in the photographic material before the beginning of drying. In accordance with this approach, the more the amount of hardening agent added is*, the shorter is the drying time. However, the reduction of the swell of the photographic material in the developer retards the progress of development, lowers the sensitivity and covering power and gives a low contrast. Further, the reduction of the swell of the photographic material in the fixing solution retards the progress of fixing, causing many troubles such as residual silver, residual hypo, residual color of sensitizing dye and worsened susceptibility to roller marks. These troubles impede the reduction of processing time.
On the other hand, in order to enhance the activity of the processing solution, it is effective to increase the content of developing agent or auxiliary developing agent in the developer and raise the pH value and the temperature of the developer. However, all these approaches deteriorate the storage stability of the processing solution, lower the contrast of image and increase fog. In order to solve these problems, it is effective to incorporate a mercapto-containing compound in the photographic material. However, this approach is disadvantageous in that it lowers the sensitivity and contrast, deteriorates the fixability and pressure properties (i.e., resistance to damage by pressure) and worsens the susceptibility to roller marks.
A technique for utilizing tabular grains for the purpose of providing adaptability to rapid processing is described in U.S. Pat. Nos. 4,439,520 and 4,425,425. JP-A-58-111933 (The term "JP-A" as used herein means an "unexamined published Japanese patent application") discloses a photographic element for radiography which comprises tabular grains to reduce the swelling ratio of the hydrophilic colloidal layer to not more than 200% to give a high covering power without adding a hardening agent during processing. Further, JP-A-63-305343 and JP-A-1-77047 disclose a technique for improving the development progress and the sensitivity/fog ratio by controlling the development starting point of silver halide grains having 111 plane to the apex and/or edge thereof and its vicinity. These known techniques are very useful methods for improving the development progress of photographic materials.
In order to obtain silver halide grains which give sufficient degree of blackening in a period of time as short as not less than 10 seconds by utilizing the foregoing techniques, a large amount of a substance which is adsorbed by silver halide, such as spectral sensitizing dye, is needed for controlling the development starting point. However, these adsorptive substances deteriorate the fixability and pressure properties and worsens the susceptibility to roller marks.
Moreover, since the automatic developing machine adapted for rapid processing essentially needs a high speed conveyance for enhancing the processing capacity, it is required that the photographic material can be easily peeled off each other and the photographic material exhibits an improved smoothness during the conveying step. On the other hand, these properties can be effectively improved by increasing the grain diameter of the matting agent. However, if the grain diameter of the matting agent on the light-sensitive layer side of a photographic material having an emulsion layer on a single side thereof such as the material for a medical CRT display is increased, the matting agent is fallen out or sinks in the film which has been developed, causing star dust-like light leak in the area uniformly irradiated with light. A typical conventional approach for avoiding such troubles is to increase the grain diameter of the matting agent on the backing layer side alone. However, a photographic material comprising matting agent grains having an increased diameter on the backing layer side can not only easily slide with but also vigorously rub against the emulsion side of another during its transportation, making the rubbed portion susceptible to desensitization or blackening (so-called abrasion or scratch). In particular, desensitization can look a focus that leads to an erroneous diagnosis which possibly results in a serious damage to both medical doctor and patient. Thus, it is difficult to improve the peelability of photographic material.